Water-borne diseases related to drinking-water
This section presents statistics on three potentially water-borne diseases in New Zealand: campylobacteriosis, giardiasis and cryptosporidiosis.
These gastrointestinal diseases cause symptoms like diarrhoea and vomiting. Contact with drinking water is one way that people may contract these diseases. Other ways include contact with contaminated recreational water, farm animals, sick animals, faecal matter, or other symptomatic people; and eating contaminated food .
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In 2016, there were 7173 notifications of campylobacteriosis, 1379 notifications of giardiasis, and 962 notifications of cryptosporidiosis (Figure 1). Campylobacteriosis cases have accounted for the majority of notified water-borne disease notifications since 2001.
These cases could have been contracted through a number of ways, not just through drinking-water. The major drop in campylobacteriosis case rates in 2007–08 is likely due to interventions to reduce contamination of poultry around this time . In August 2016, a campylobacteriosis outbreak in Havelock North due to contaminated drinking-water accounted for a substantial increase in notifications.
In 2016, there were 1466 notifications of campylobacteriosis, 222 notifications of giardiasis, and 242 notifications of cryptosporidiosis that reported drinking untreated water during the incubation period.
However, risk factor information was only collected for a proportion of notifications, so these numbers may be an underestimate. In particular, risk factor information was collected for only 42% of campylobacteriosis notifications, 45% of giardiasis notifications, and 68% of cryptosporidiosis notifications. Risk factor completion rates varied substantially by District Health Board.
In 2012-16, the following District Health Boards (DHBs) had higher rates of campylobacteriosis, giardiasis and/or cryptosporidiosis with a risk factor of drinking untreated water:
- Hawke's Bay DHB
- West Coast DHB
- Wairarapa DHB
- Tairawhiti DHB
- Northland DHB
- Waikato DHB.
See the factsheets for more information (available from the downloads section).
Information about the data
Notifications of campylobacteriosis, cryptosporidiosis and giardiasis
Source: Institute of Environmental Science and Research (ESR)
This section presents the number of notifications of campylobacteriosis, giardiasis and cryptosporidiosis.
- It excludes people who had been overseas during the incubation period, as they were unlikely to be infected in New Zealand.
- Notifications of diseases may underestimate the true number of cases of diseases, as not everyone will go to a doctor when sick.
- Cases that had been overseas during the incubation period were excluded as they were unlikely to be infected in New Zealand.
- Not every case reported a ‘risk factor’ (such as untreated drinking water and recreational water contact). The reported number of water-borne disease cases by risk factor is smaller than the actual number.
- Sears A, Baker MG, Wilson N, Marshall J, Muellner P, Campbell DM, et al. 2011. Marked campylobacteriosis decline after interventions aimed at poultry, New Zealand. Emerging Infectious Diseases. 17(6).
- ESR. 2015. Notifiable and Other Diseases in New Zealand: Annual Report 2014. Porirua: The Institute of Environmental Science and Research. Available online: https://surv.esr.cri.nz/surveillance/annual_surveillance.php